title: Anti-NKG2A autoantibodies in a patient with systemic lupus erythematosus.
abstract: OBJECTIVE
  To characterize a novel anti-NKG2A autoantibody detected in a patient with SLE during a severe flare, and in a cross-sectional study investigate the occurrence of such autoantibodies in patients with SLE and primary SS (pSS).
  
  
  METHODS
  Serum or IgG from patients with SLE, pSS and healthy volunteers were assayed for blocking of anti-NKG2A or HLA-E binding to peripheral blood mononuclear cells or CD94/NKG2A- and CD94/NKG2C-transfected Ba/F3 cells. The anti-NKG2A autoantibodies were evaluated for effect on NK cell degranulation in response to HLA-E-transfected K562 cells. IFN-α was determined by an immunoassay and disease activity by the SLEDAI score.
  
  
  RESULTS
  Anti-NKG2A autoantibodies, which blocked binding of HLA-E tetramers to CD94/NKG2A-transfected cells and impaired NKG2A-mediated inhibition of NK cell activation, were observed in a patient with SLE. The presence of anti-NKG2A autoantibodies was associated with high SLE disease activity (SLEDAI score 14 and 16) and increased serum IFN-α. Of 94 SLE, 60 pSS and 30 healthy donor sera, only the index patient serum contained anti-NKG2A autoantibodies.
  
  
  CONCLUSIONS
  The presence of autoantibodies targeting NKG2A is a rare event, but when such autoantibodies occur they may promote excessive NK cell function. This can contribute to the pathogenesis by increasing the killing of cells and the release of autoantigens. Our findings highlight the possible importance of NK cells in the SLE disease process.
authors.affiliation: Department of Medical Sciences, Section of Rheumatology, Systemic Autoimmunity Group, Clinical Research Department 3, Entrance 85 3rd Floor, 751 85 Uppsala, Sweden. niklas.hagberg@medsci.uu.se.
authors.forename: Niklas
authors.initials: N
authors.lastname: Hagberg
authors.forename: Jakob
authors.initials: J
authors.lastname: Theorell
authors.forename: Maija-Leena
authors.initials: ML
authors.lastname: Eloranta
authors.forename: Veronique
authors.initials: V
authors.lastname: Pascal
authors.forename: Yenan T
authors.initials: YT
authors.lastname: Bryceson
authors.forename: Lars
authors.initials: L
authors.lastname: Rönnblom
mesh_terms: D001323:Autoantibodies / Q000097:blood*; D015550:Cell Degranulation / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D006801:Humans; D016898:Interferon-alpha / Q000097:blood; D007694:Killer Cells, Natural / Q000276:immunology; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D008297:Male; D055654:NK Cell Lectin-Like Receptor Subfamily C / Q000276:immunology*; D055815:Young Adult; D000097625:HLA-E Antigens
chemical_list: D001323:Autoantibodies; D015395:Histocompatibility Antigens Class I; D016898:Interferon-alpha; D055654:NK Cell Lectin-Like Receptor Subfamily C; D000097625:HLA-E Antigens
keywords: HLA-E; NKG2A receptor; Sjögren’s syndrome; autoantibodies; autoimmunity; systemic lupus erythematosus